AU725613B2

AU725613B2 - Installing pipes

Info

Publication number: AU725613B2
Application number: AU54025/98A
Authority: AU
Inventors: Stephen Robert Delaforce
Original assignee: BG PLC; British Gas PLC
Current assignee: BG Group Ltd
Priority date: 1996-12-05
Filing date: 1997-12-04
Publication date: 2000-10-12
Anticipated expiration: 2017-12-04
Also published as: WO1998025070A1; US6102624A; BR9713827A; GB2320078A; CA2274052A1; AR014577A2; JP2000512000A; GB9625365D0; GB2320078B; AR010676A1; EP0953125A1; EP1134477A1; AU5402598A; RU2166146C2; GB9709218D0

Description

WO 98/25070 PCT/GB97/03355 Installing Pipes The present invention relates to a method and apparatus for installing a replacement pipe in an existing service pipe.

The invention is particularly, but not solely, applicable to the installation of a service pipe of plastics material in an existing gas service pipe of steel.

GB-2227071 discloses a method for installing a plastics service pipe in an existing steel service pipe which extends from a main pipe to a meter within a consumer's premises. Firstly the meter is removed: then the plastics pipe is inserted through a gland fitted to the open end of the existing service pipe and advanced along the service pipe up to a point adjacent the junction of the service pipe with the main pipe. The plastics pipe has a sealing head.fitted to its leading or forward end, which closes that end of the pipe and also seals against the interior of the existing service pipe. Once the plastics pipe has been advanced to the required position, fluid sealant is fed into the annular space between the exterior of the plastics pipe and the interior surface of the existing service pipe.

The sealant is allowed to set, and then a flexible rod having a pointed end is advanced along the plastics pipe to break the seal across its forward end and open the replacement pipe for the flow of gas from the main pipe.

The above-described method is applicable to low pressure systems, in which therefore the force acting on the sealing head, as the plastics pipe is advanced into the existing service pipe, is relatively small: accordingly, the plastics pipe can be advanced manually without difficulty. However, for higher pressure systems, for example systems operating at pressures up to 7 bar, the resulting force acting on the sealing head at the forward end of the plastics pipe would be too high to permit the plastics pipe to be advanced manually along the existing service pipe.

GB-22996 4 5 discloses methods for installing a replacement plastics pipe in an existing steel service pipe, which methods are suitedto use on systems which operate at high pressures. In these methods, a seal is advanced along the existing service pipe using an elongate flexible assembly, but the seal is not deployed until it reaches the required position. Some embodiments require the seal to be advanced beyond the far end of the existing service pipe, where it joins the main pipe, and then deployed to engage against the end of the service pipe: however, it is not always possible or convenient to achieve this and the seal may not be wholly effective, for example if the end of the pipe is damaged. Other embodiments require that the elongate flexible assembly advances the plastics replacement pipe along the existing service pipe at the same time as it advances the seal into position, and therefore before the seal is deployed: however, this can lead to difficulties in advancing the replacement pipe against the full normal operating pressure.

In accordance with the present invention there is provided a method of installing a replacement pipe within an existing pipe, the method comprising the steps of advancing a sealing means along said existing pipe from one end thereof and then deploying said sealing means, once it has been advanced to a desired position, to seal against the interior surface of the existing pipe, subsequently advancing said replacement pipe along said existing pipe from AMENDED

SHEET

IPENEP

-3of advancing a sealing means along said existing pipe from one end thereof and then deploying said sealing means, once it has been advanced to a desired position, to seal against the interior surface of the existing pipe, subsequently advancing said replacement pipe along said existing pipe from said one end of the latter, introducing sealant material into the space between said replacement pipe and said existing pipe, and opening said sealing means, an elongate flexible guide being used to advance said sealing means to its said desired position, and said step of opening said sealing means comprising withdrawing said guide element, and characterised in that a frangible seal between a body part of said sealing means and said guide element, or a collar on said guide element, is broken upon withdrawal of said guide element, to open said sealing means.

i 4**4 9*o* 9• .9.o 9 o 4 According to another aspect of the invention there is provided apparatus for installing a replacement pip within an existing pipe according to the method of the first aspect of the invention, said apparatus comprising a seal body, an elongate flexible guide element for advancing the seal body along said existing pipe to a desired position, means for cooperating with the seal body along said existing pipe including means for introducing sealant material into the space between the replacement pipe and the existing pipe, and a frangible seal between a body part of said sealing means and the guide element or a collar on the guide element for opening the sealing means on withdrawal of the guide element following introduction of the replacement pipe and sealant material.

S 15 The apparatus may include means for introducing sealant material into an annular space between the periphery of said seal body and the interior surface of p said existing pipe.

oeoo he apparatus may include radially inner and outer seal bodies, the outer seal body being arranged to seal against the interior surface of the existing pipe and the inner seal body being arranged to engage within the outer seal body upon axial displacement of the two seal bodies relative to each other.

The apparatus may be configured so that the seal body for sealing against the interior surface of the existing pipe has apertures therethrough, and an element is provided which is rotatable relative to said seal body to close said apertures.

The apparatus may comprise first and second seal bodies to which respective annular elements are mounted, said first and second seal bodies being axially displaceable relative to each other to deflect said annular elements radially outwards to engage the interior surface of said existing pipe.

The apparatus may include two annular seal bodies supporting an annular seal between them, said seal being deformed radially outwards upon relative axial displacement of said two seal bodies.

Embodiments of the present invention will now be described by way of examples only and with reference to the accompanying drawings, in which: ~~1 WO 98/25070 PCT/GB97/03355 6 FIGURES 1 to 6 are schematic longitudinal sectional views of an end portion of an existing service pipe, showing successive stages in the installation of a replacement pipe in accordance with a first embodiment of the invention; FIGURES 7 to 11 are similar views of the service pipe, showing successive stages in the installation of the replacement pipe in accordance with a second embodiment of the invention; FIGURE 12 is a similar view to Figure 10, showing the use of a modified nose cone at the leading end of the replacement pipe; FIGURES 13 to 19 are schematic longitudinal sectional views of the end portion of the existing service pipe, showing successive stages in the installation of the replacement pipe in accordance with a third embodiment of the invention; FIGURES 20 to 24 are similar views of the service pipe, showing successive stages in the installation of the replacement pipe in accordance with a fourth embodiment of the invention; FIGURES 25 to 30 are similar views of the service pipe, showing successive stages in the installation of the replacement pipe in accordance with a fifth embodiment of the invention; FIGURES 31 to 36 are similar views of the service pipe, showing successive stages in the installation of the replacement pipe in accordance with a sixth embodiment of the invention; FIGURES 37 to 43 are similar views of the service pipe, showing successive stages in the installation of the replacement pipe in accordance with a seventh embodiment of the invention; FIGURES 44 to 50 are similar views of the service pipe, showing successive stages in the installation of the replacement pipe in accordance with an eighth embodiment of the invention; WO 98/25070 PCT/GB97/03355 7 FIGURES 51,to 57 are similar views of the service pipe, showing successive stages in the installation of the replacement pipe in accordance with a ninth embodiment of the invention; and FIGURES 58 to 64 are similar views of the service pipe, showing successive stages in the installation of the replacement pipe in accordance with a tenth embodiment of the invention.

Referring to Figure 1 of the drawings, there is shown an end portion of a steel service pipe 1 where it enters a main pipe 2 through an aperture in the wall of the latter. The main pipe carries gas at pressures up to 7 bar, and in normal use gas flows from the main pipe 2 and along the service pipe 1 to a consumer's installation. In order to install a replacement pipe into the steel service pipe i, the consumer's end of the service pipe 1 is made accessible and fitted with a sealing arrangement (for example as disclosed in GB-2227071): this sealing arrangement maintains the consumer's end of the service pipe closed against the flow of gas, but enables selected components (as will be described below) to be inserted into that end of the service pipe for advancement along it.

As shown in Figure i, an elongate flexible guide rod 5 is inserted into the service pipe 1 at the consumer's end and advanced along the service pipe 1 until it reaches the junction with the main pipe 2. The guide rod 5 carries, adjacent its forward end, a collar 7 which in turn carries an annular seal body 6. Two ring seals 8 are mounted at axially-spaced positions on the exterior of the seal body 6, to co-operate with the interior surface of the service pipe 1: however, the ring seals 8 form only a light sealing function and do not prevent high pressure gas from flowing over them and accordingly the assembly of guide rod 5, its collar 7 and seal body 6 do not experience any high resistance against being advanced manually along the service pipe 1 to the position shown.

WO 98/25070 PCT/GB97/03355 8 In the next stage, as shown in Figure 2, sealant is pumped along a tube 9, connected to the trailing or rear end of the collar 7, and through a passage in the collar 7, into the annular space 10 between the seal body 6 and the interior surface of the service pipe i: the sealant is confined, in the axial direction, by the ring seals 8. The tube 9 is then disconnected from the collar 7 by unscrewing) and withdrawn and the sealant is allowed to cure. Once'set, the sealant holds the collar 7 and seal body 6 in position against the pressure of gas in the main pipe 2.

At this stage, the consumer's end of the service pipe 1 is opened and the replacement pipe 11 is inserted and advanced along it (Figure The replacement pipe 11 is a plastics pipe which is circumferentially corrugated to provide flexibility. A tubular guide 13, in the form of a helical coil of wire, lies within the replacement pipe 11 and carries a thrust ring 12 adjacent its forward end, which engages the interior of the replacement pipe 11 adjacent its forward end.

The tubular guide 13 is engaged over the guide rod 5, and is manually advanced, pushing the replacement pipe 11 with it, until the forward end of the replacement pipe 11 locates within a socket defined by an annular rim 7a on the rear end of the collar 7. Then, as shown in Figure 4, sealant 14 is introduced to fill the space between the exterior of the replacement pipe 11 and the interior surface of the service pipe i.

Once the sealant 14 has cured, the tubular guide 13 is withdrawn (Figure and then the guide rod 5 and collar 7 are withdrawn, leaving the seal body 6 in position (Figure 6) and allowing mains gas to flow into the replacement pipe. The collar 7 may be connected to the seal body 6 by a frangible seal, which is broken by pulling on the guide rod 5. It will be appreciated that before the guide rod 5 and collar 7 are withdrawn, the sealing arrangement must be refitted to the consumer's end of the service pipe.

Figures 7 to 11 show the successive stages of a similar method WO 98/25070 PCT/GB97/03355 9 of installing the replacement pipe 11 in the service pipe i.

As shown in Figure 7, the flexible guide rod 5 carries a collar to which an annular shape-memory seal 16 is mounted. Once the guide rod 5 has been advanced to position the seal 16 adjacent the end of the service pipe 1, the seal 16 is caused to recover its shape (Figure in which recovered shape it seals against the interior surface of the service pipe i. The recovery in shape of the seal 16 is caused by the application of heat e.g. by an electrical heat source (not shown).

Next, as shown in Figure 9, the replacement pipe 11 is advanced along the service pipe i, using the tubular guide 13 which is slid along the guide rod 5. In this case, an annular nose cone 17 is carried on the end of the tubular guide 13 and the end of the replacement pipe 11 seats on the rear end of the nose cone. The tubular guide 13 is advanced until the forward end of the nose cone 17 locates around the collar 15. Then the sealant 14 is introduced into the space around the replacement pipe 11 and allowed to cure (Figure 10). Finally, the guide rod 5 is withdrawn, breaking a frangible seal between the collar 15 and the seal 16 and so withdrawing the collar 15 and also the tubular guide 13 (Figure 11) In the modification shown in Figure 12, the nose cone 17 is provided with an annular seal 18 spaced rearwardly of its forward end, and arranged to seal against the interior surface of the service pipe 1 and limit the forward flow of the sealant 14.

Figures 13 to 19 show the successive stages of the third embodiment for installing the replacement pipe 11. In this case (Figure 13), a tubular seal body 21 has a forward end mounted to a collar 23 fitted onto the guide rod 5: an annular seal 23 is carried on the outside of the seal body 21, adjacent its rear end. Once the guide rod 5 has been advanced to the desired position, the tubular guide 13 is advanced: a nose cone 20 is fitted to the forward end of the tubular guide 13 WO 98/25070 PCT/GB97/03355 and is arranged to enter the rear end of the seal body 21 and so radially expand the latter to cause the annular seal 23 to engage and seal against the interior surface of the service pipe 1 (Figure 14): the nose cone 20 and seal body 21 are arranged to interlock so as to remain together. Then the tubular guide 13 is withdrawn (Figure Next, the thrust ring 12 is fitted to the tubular guide 13 and the assembly is positioned within the replacement pipe 11.

Then, as described with reference to Figure 3, the replacement pipe 11 is advanced into the service pipe 1, the tubular guide 13 sliding along the guide rod 5, until the forward end of the replacement pipe 11 locates within a socket formed on the rear end of the nose cone 20 (Figure 16) In the next stage, the sealant 14 is introduced to fill the space around the replacement pipe 11 (Figure 17). Then the tubular guide 13 and thrust ring 12 are withdrawn (Figure 18) and finally the guide rod 5 and its collar 22 are withdrawn (Figure 19) to open the replacement pipe to the mains.

The fourth embodiment of the invention will now be described with reference toFigures 20 to 24 of the drawings. As shown in Figure 20, the guide rod 5 carries a collar 33 which in turn carries an annular seal body 34, to which an inflatable annular seal 35 is mounted. A replacement pipe 30 is carried over the guide rod 5 and has its forward end secured around the seal body 34. The replacement pipe 30 is flexible and is of a reduced cross-sectional configuration, except for its forward end portion. For example, the pipe 30 may be a shape-memory plastics pipe in a flattened configuration; in another example, it may be a pipe deformed into a flattened or U-section.

A

feed tube 31 is also disposed within the pipe 30 and is connected to the seal body 34. The assembly of guide rod replacement pipe 30 and feed tube 31 are advanced together into the service pipe 1 to reach the position shown in Figure WO 98/25070 PCU/GB97/03355 11 Then an appropriate fluid nitrogen or other inert gas) is passed through the feed tube 31 and a one-way valve (not shown) provided in the seal body 34, to inflate the seal into engagement with the interior surface of the service pipe 1, as shown in Figure 21. Next the feed tube 31 is disconnected from the seal body 34, and is then used to pressurise the interior of the replacement pipe 30 to reform the latter to its required, expanded configuration as shown in Figure 22: if the replacement pipe is a shape-memory pipe, the application of heat may be necessary to recover it.

In the next stage, the sealant 14 is introduced to fill the space around the replacement pipe 30 (Figure 23) Finally, the guide rod 5 and its collar 33 are withdrawn (Figure 24) to open the replacement pipe 30 to the mains 2.

The fifth embodiment will now be described with reference to Figures 25 to 30 of the drawings. Firstly, the guide rod 5 and the tubular guide 13 are advanced together along the service pipe 1. The guide rod 5 carries a collar 43 which carries an annular seal body 44 fitted with an annular seal 45 around its periphery. Tubular guide 13 carries a collar 40 having three radial arms 40a to which an annular outer seal body 41 is coupled, the latter body having an annular seal 42 around its periphery. Whilst being advanced into the service pipe i, the outer seal body 41 is spaced rearwardly of the inner seal body 44 so that gas is able to flow past the assembly. Then, as shown in Figure 26, the tubular guide 13 is slid forwardly on the guide rod 5 (or the guide rod 5 is retracted relative to the tubular guide 13) to engage the outer seal body 41 around the inner seal body 44. A seal is thus formed across the service pipe 1, the seal 45 sealing between the inner and outer seal bodies and the seal 42 sealing between the outer seal body 41 and the service pipe 1. Next the tubular guide 13 is withdrawn, bringing with it the collar 40 (Figure 27).

In the next stage (Figure 28), the replacement pipe 11 is WO 98/25070 PCT/GB97/03355 12 advanced into the service pipe 1, using the tubular guide 13 and a nose cone 46, as described above with reference to Figure 9, until the forward end of the nose cone 46 engages around the collar 43. Then the sealant 14 is introduced to fill the space around the replacement pipe 11 (Figure 29) and finally the guide rod 5, its collar 43 and the tubular guide 13 are removed (Figure The sixth embodiment will now be described with reference to Figures 31 to 36 of the drawings. In this case, the guide rod carries a collar 50 around which a seal arrangement 51,52 is mounted. This seal arrangement comprises a first disc 51 which seals against the interior surface of the service pipe 1 but is formed with a number of sector-shaped apertures, and a second disc 52 mounted face-to-face with the first disc 52 and formed with corresponding sector-shaped apertures. During advancement of the guide rod 5, the second disc 52 is turned so that its apertures are aligned with those of the first disc 51, so that the seal arrangement is open for the flow of gas.

Then, the second disc 52 is turned relative to the first disc 51 using an actuating mechanism (not shown), to close the seal arrangement (Figure 32).

Next, referring to Figure 33, the replacement pipe 11 is advanced along the service pipe i, using the tubular guide 13 and a nose cone 50, in the manner described with reference to Figure 9. The sealant 14 is then introduced into the space around the replacement pipe 11 (Figure 34). Finally, the tubular guide 13 is withdrawn (Figure 35), following by the guide rod 5 and its collar 50 (Figure 36).

The seventh embodiment of the invention will now be described with reference to Figures 37 to 43 of the drawings. The guide rod 5 and tubular guide 13 are advanced together along the service pipe 1 (Figure 37). The guide rod 5 carries a collar which carries an outer seal body 61 having a peripheral seal 62 which seals against the interior surface of the service pipe WO 98/25070 PCT/GB97/03355 13 1: the outer seal body 61 is annular in shape and includes radial arms 61a by which it is mounted to the collar 60. The tubular guide 13 carries a collar 65 which carries an inner seal body 63 provided with a peripheral seal 64. Whilst the guide rod 5 and tubular guide 13 are advanced, the inner seal body 65 remains at a spacing to the rear of outer seal body 61, so that the gas is able to flow past.

When the outer seal body 61 has reached the required position, the tubular guide 13 is slid forwardly on the guide rod 5 (or the guide rod is retracted relative to the tubular guide 13) to insert the inner seal body 63 into the centre of the annular outer seal body 61 (Figure 38). A seal is thus formed across the service pipe 1, the seal 64 sealing between the two seal bodies and the seal 62 sealing the outer seal body against the interior of the service pipe i.

Next the tubular guide 13 is withdrawn (Figure 39). The replacement pipe 11 is then advanced using the tubular guide 13 and a nose cone 66 (Figure 40), in the manner previously described with reference to Figure 9, until the front end of the nose cone 66 locates around a rearwardly-projecting end portion of the inner seal body 65. Then the sealant 14 is introduced to fill the space around the replacement pipe 11 (Figure 41). Finally, the tubular guide 13 is withdrawn (Figure 42), followed by the guide rod 5 and collars 60 and to which the respective seal bodies 61,63 are frangibly connected (Figure 43).

The eighth embodiment of the invention will now be described with reference to Figure 44 to 50 of the drawings. In this case, as shown in Figure 44, the guide rod 5 carries an inflatable body 70 to which a feed pipe 72 is connected. Once the guide rod 5 has been advanced as required, the body 70 is inflated by feeding fluid nitrogen or other inert gas) under pressure through the pipe 72 and through a one-way valve of the body 70, to cause the inflated body 70 to seal against WO 98/25070 PCT/GB97/03355 14 the interior surface of the service pipe 1 (Figure 45). Then the feed pipe 72 is disconnected and withdrawn. In the next stage (Figure 46), the tubular guide 13 is used to advance the replacement pipe 11, the forward end of the tubular guide 13 carrying a collar 73 around which the forward end of the replacement pipe 11 is fitted. Next the sealant 14 is introduced to fill the space around the replacement pipe 11 (Figure 47) Finally, the tubular guide 13 is withdrawn (Figure 48), the body 70 is deflated (Figure 49), for example via a passage extending through the guide rod 5, and the guide rod 5 and deflated body 70 are withdrawn (Figure The ninth embodiment of the invention will now be described with reference to Figures 51 to 57 of the drawings. As shown in Figure 51, the guide rod 5 and tubular guide 13 are advanced together along the service pipe 1. The guide rod 5 carries a collar 84 and the tubular guide 13 carries a collar 83. An annular seal 81 is mounted to the collars 84,83 by means of respective annular carrier elements 80,80a. Once the required position within the service pipe 1 has been reached, the tubular guide 13 is slid forwardly on the guide rod 5 (or the guide rod 5 is retracted) to bring the collar 83 closer to the collar 84, so deflecting the annular carrier elements 80,80a radially outwards, and expanding the seal 81 into engagement with the interior surface of the service pipe 1 (Figure 52) As shown, an over-centre position is reached, so that the tubular guide 13 can then be withdrawn (Figure 53) whilst the collar 83 remains locked in its forward position.

In the next stage (Figure 54), the tubular guide 13 is used, together with a nose cone 86, to advance the replacement pipe 11 into position, as previously described with reference to Figure 9, until the forward end of the nose cone 86 locates over the collar 83 (Figure 54) The sealant 14 is now introduced to fill the space around the replacement pipe 11 and WO 98/25070 PCT/GB97/03355 allowed to set (Figure 55). Finally, the tubular guide 13 is withdrawn (Figure 56), followed by the guide rod 5 together with the collars 84,83 (Figure 57) The tenth embodiment of the invention will now be described with reference to Figures 58 to 64 of the drawings. In this case, the guide rod 5 and tubular guide 13 are advanced together along the service pipe 1 (Figure 58). The guide rod carries a collar 90: the collar 90 and the forward end of the tubular guide 13 carry rigid annular seal plates 91,92 respectively, via mounting flanges 91a,92a of these plates.

A seal 93 is mounted between the outer peripheral edges of these two seal plates. When the assembly has reached the required position within the service pipe 1, the tubular guide 13 and guide rod 5 are moved axially relative to each other to bring the seal plates 91,92 together, so deforming the seal 93 radially outwards to seal against the interior surface of the service pipe 1 (Figure 59). A self-locking arrangement (not shown) is provided so that the seal plates 91,92 remain locked together: this arrangement may comprise catches projecting from one plate and arranged to latch into sockets on the other plate; alternatively, one or both of the plates may be precoated with adhesive so that the plates adhere together when brought into contact.

Next, the tubular guide 13 is withdrawn (Figure 60) and is then used, together with a nose cone 94, to advance the replacement pipe 11, until the forward end of the nose cone 94 locates over the mounting flange 92a of the seal plate 92 (Figure 61). The sealant 14 is then introduced to fill the space around the replacement pipe 11 (Figure 62). Finally, the tubular guide 13 is withdrawn (Figure 63) and then the guide rod 5 is withdrawn together with its collar 90 (Figure 64)

Claims

1. A method of installing a replacement pipe within an existing pipe, the method comprising the steps of advancing a sealing means along said existing pipe from one end thereof and then deploying said sealing means, once it has been advanced to a desired position, to seal against the interior surface of the existing pipe, subsequently advancing said replacement pipe along said existing pipe from said one end of the latter, introducing sealant material into the space between said replacement pipe and said existing pipe, and opening said sealing means, an elongate flexible guide being used to advance said sealing means to its said desired position, and said e. 15 step of opening said sealing means comprising withdrawing o said guide element, and characterised in that a frangible seal between a body part of said sealing means and said guide element, or a collar on said guide element, is broken upon withdrawal of said guide element, to open said 20 sealing means. eooe

2. A method as claimed in claim 1, in which said sealing means is deployed by feeding sealant into an annular space between a seal body of said sealing means and the interior 25 surface of said existing pipe. i•

3. A method as claimed in claim i, in which said sealing means comprises a shape-memory seal and is deployed by recovery of said seal to engage the interior surface of said existing pipe.

4. A method as claimed in claim I, in which said sealing means is deployed by effecting relative displacement of two parts thereof axially of said existing pipe.

A method as claimed in claim 4, in which respective- T2_Said parts of said sealing means are carried on concentric (n 17 elongate flexible guide elements.

6. A method as claimed in claim 4 or 5, in which a first part of said sealing means comprises a tubular body which is radially expanded into sealing engagement with said existing pipe by relative displacement of the second part of the sealing means into one end of said tubular body.

7. A method as claimed in claim 4 or 5, in which said two parts of the sealing means comprise radially inner and outer seal bodies, the inner seal body engaging within the outer seal body in order to deploy said sealing means.

8. A method as claimed in claim 4 or 5, in which said 15 sealing means comprises two annular elements which are :ooo e .mounted to respective said parts of the sealing means and are deflected radially outwards upon said relative displacement of said parts.

9. A method as claimed in claim 4 or 5, in which said two parts of the sealing means comprise annular elements 9 9 supporting an annular seal between them, said seal being deformed radially outwards upon said relative displacement 9.9 of said parts. "9

10. A method as claimed in claim i, in which said sealing 9 o• means is deployed by effecting relative rotation of two parts thereof around the axis of said existing pipe.

11. A method as claimed in claim 1, in which said sealing means is deployed by inflating an inflatable body thereof into engagement with the interior surface of said existing pipe.

12. A method as claimed in any preceding claim, in which said replacement pipe is advanced along said existing pipe until its forward end engages in a socket provided at the 9- a )u 18 rear end of a body part of said sealing means.

13. A method as claimed in any one of claims 1 to 11, in which said replacement pipe carries an annular fitment at its forward end, and said replacement pipe is advanced along said existing pipe until the forward end of said annular fitment engages around a body part of said sealing means.

14. A method as claimed in any preceding claim, in which said replacement pipe is advanced along said existing pipe using an elongate flexible guide means extending within said replacement pipe and coupled to the forward end of said replacement pipe.

15. Apparatus for installing a replacement pipe within an c '"existing pipe according to the method claimed in claim i 0in which an existing pipe is sealed in the installation process, said apparatus comprising a seal body, an elongate flexible guide element for advancing the seal body along said existing pipe to a desired position, means for co-operating with the seal body along said existing pipe including means for introducing sealant material into o. 0 the space between the replacement pipe and the existing 25 pipe, and a frangible seal between a body part of said o sealing means and the guide element or a collar on the guide element for opening the sealing means on withdrawal of the guide element following introduction of the replacement pipe and sealant material.

16. An apparatus as claimed in claim 15, including means for introducing sealant material into an annular space between the periphery of said seal body and the interior surface of said existing pipe.

17. An apparatus as claimed in claim in which the periphery of said seal body is provided with an annular 19 channel to receive said sealant.

18. An apparatus as claimed in claim 15, including a shape-memory seal body arranged, upon recovery, to expand radially into sealing engagement with the interior surface of said existing pipe.

19. An apparatus as claimed in claim 15, wherein the seal body is arranged for fitment thereto of the forward end of the replacement pipe, and having a seal for radial expansion into sealing engagement with the interior surface of the existing pipe. 0000 S20. An apparatus as claimed in claim 15, including 15 radially inner and outer seal bodies, the outer seal body being arranged to seal against the interior surface of the existing pipe and the inner seal body being arranged to 0 engage within the outer seal body upon axial displacement of the two seal bodies relative to each other.

OQ

21. An apparatus as claimed in claim 15, wherein the seal body for sealing against the interior surface of the ".existing pipe having apertures therethrough, and an element which is rotatable relative to said seal body to close said apertures.

22. An apparatus as claimed in claim 15, comprising first and second seal bodies to which respective annular elements are mounted, said first and second seal bodies being axially displaceable relative to each other to deflect said annular elements radially outwards to engage the interior surface of said existing pipe.

23. An apparatus as claimed in claim 15, including two-- annular seal bodies supporting an annular seal between them, said seal-being deformed radially outwards upon relative axial displacement of said two seal bodies. 20

24. A method substantially as herein described with reference to the accompanying drawings. An apparatus substantially as herein described with reference to the accompanying drawings. 0 0000 00 0 00 00 0 0 *0*0 S 0004 S *000 00 0 S 00 0 *00 0 *000 0 S 5050 S 0050 00 0 0 0 0 S. 5000 0 0 OqOS OS 0 00 0O SO S 05 50